The invention relates to an electronic central locking system for motor vehicles and operating systems for locks or the like whose actuating elements are connected, such that they can be switched, via supply voltage lines to a controller.
In a known central locking system for motor vehicles, operating points which are designed as infrared receivers or else as receivers for other wire-free signals are constructed on the doors, on the trunk lid and in the vicinity of the starter switch as well as on the filler cap lock.
These operating points are all the same in the known central locking system. Each operating point comprises a transmitting device which includes a modulator, an amplifier and an IR diode, and a receiving device having a photo diode, an amplifier and a demodulator. Each of these operating points is connected via in each case two supply voltage lines to a controller, which essentially comprises a microcomputer and an interface circuit (DE-A 36 28 706 A1).
It is disadvantageous that this known central locking system is not thief-proof since the actuating elements can be changed to the xe2x80x9copenxe2x80x9d position by applying external voltages to the supply voltage lines.
In contrast to this, the invention is based on the object of improving a central locking system of the described type such that it is thief-proof.
It has been found that this object can be achieved in a simple manner by arranging a switch, which can be switched by coded signal, in the supply voltage lines for driving an actuating element.
According to a feature of the invention, the switch which can be switched by the coded signal is arranged in the immediate vicinity of the drive for an actuating element.
This means that application of an external voltage to a supply voltage line cannot operate the drive for an actuating element, since the supply voltage line is interrupted by the switch immediately upstream of the drive. The actuating element cannot be influenced until the switch in the supply voltage line has been closed by the correct coded signal.
The coded signals for the switches can reach said switches via signal lines which are arranged between the controller and the switches.
According to another feature of the invention, the coded signals can alternatively be transmitted to a switch via the supply voltage line for the drive for the actuating element.
It is advantageous if, according to still another feature of the invention, the drive for an actuating element, the switch and the switching electronics are combined to form a unit. An economic and simple circuit is provided by using the voltage supply for the unit both for supplying the switching electronics and for supplying the drive for the actuating element.
In a second exemplary embodiment, the drives for the actuating elements are driven by data signals which pass via dedicated data lines to the switches and to the switching electronics in order to drive the drives for the actuating elements.
According to other features of the invention, pulse modulation or amplitude modulation can be mused to apply the coded signals to the supply voltages.
In order to improve the security to prevent theft, the voltage supply lines and/or the signal and data lines are laid in a concealed manner.